Demagnetizers and methods for demagnetizing



June 21, 1960 M c, BECKER 2,942,162

DEMAGNETIZERS AND METHODS FOR DEMAGNETIZING Filed July 2. 1953 TEE 1.

15 17 1a Z2 7 15 13 i 5% {zflalulzz fL United States Patent Gmce Patented June 21, 1960 DEMAGNETIZERS AND METHODS FOR DEMAGNETIZING C. Becker, 79 Washingtnn St., East Orange, NJ.

Maximilian This invention relates to novel methods and apparatus for the purposes of demagnetization. In one of its specific aspects the invention is directed to novel methods and apparatus for demagnetizing that class known as permanent magnets and also that class which is not in the permanent magnet class but consists of materials which retain a very small amount of residual magnetism after having been in a magnetic field. The first class of materials are the magnetized alloys and also ceramic permanent magnet materials containing various elements in different proportions and are characterized by having relatively high remanence and coercive force characteristics and examples of some of them are known on the market as Alnico l-Xll, lndalloy," Cunife, Indox 1, etc. The second class are ferrous metals, such as soft iron, steel, etc. which have been subjected to a magnetic field and then removed therefrom. 1

The main object of this invention is to provide a very simple and cheap apparatus of rugged design which may be cheaply operated and maintained and to provide a simple and inexpensive method for demagnetizing.

Briefly, the apparatus of this invention comprises a coil having a relatively few number of turns of electrical conducting wire in series with filamentary incandescent lamps which may consist of one or more of such lamps in parallel to provide a lamp bank which is in series with a switch for making and breaking a circuit through conductors; such as a male plug adapted to becoupled with a live female socket, of the customary 110 or 220 volt alternating current source of supply. One or more of such coils may be located adjacent against the object to be demagnetized; then the switch is actuated to make the circuit whereupon an electric current of high amperage value passes through said coil for only a very short period of time and decays to normal, thus subjecting said object to a very high alternating flux field rapidly decaying to normal whereby said object is demagnetized. Since the coil has relatively few turns it has low inductance, hence the flux build up is rapid.

'Theinvention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features combinations of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the, nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic view of an embodiment of the novel apparatus of this invention and illustrates a relation of the coil to the object to be demagnetized.

Fig. 2 is a view similar to Fig. l and illustrates a modifica-non ofthe embodiment of Fig. 1. r

Fig. 3 is a view similar to Fig. 1 and illustrates another modification of the embodiment of Fig. 1.

Fig. 4 is a diagrammatic view illustrating a toroidal shaped coil surrounding the element to be demagnetized.

Fig. 5 is a diagrammatic view of a toroidal shaped coil surrounding a horse shoe element to be demagnetized.

The apparatus shown in Fig. 1 is a novel, simple and inexpensive apparatus for practicing a novel method of this invention. As shown in Fig. 1, the apparatus comprises a coil 10, one end of which is connected to one side of a switch 12 through a conductor 13. The other side of switch 12 is connected to a male contact 15 of a male plug 16 through conductor 17. The other side of coil 10 is connected through conductor 18 to-one side of a bank of filamentary so-called incandescent lamps 20 arranged in parallel, with each lamp having a switch 21 for making it part of a circuit. Theother side of the bank of lamps 20 is connected through conductor 23 to the other contact 15 of plug 16. The extent of lamp resistance in the circuit may be varied by closing the appropriate number of switches 21 and by employing such lamps of appropriate resistance or rated wattage. For example, the lamps 20 :may all be those which are rated at 250 watts at volts, and with all switches 21 closed a predetermined resistance is in the circuit. Instead of employing such a design, a single lamp rated at 1000 watts at 110 volts may be used with only its switch 21 closed. It is to be understood that lamps of any desired resistance or rated wattage may be used and that the number of them may be one or any other number which is practical and desired. The lamps 20 employed are those which are commonly known on the market as incandescent lamps and are tungsten filament lamps. Such lamps have a low resistance at room temperature and high resistance at incandescent temperature.

In operation the coil 10 which consists of few'number of turns extends around and substantially completely surrounds lengthwise an element 40 which is to be demagnetized. Theelement 40 may be a permanent magnet composed of permanently magnetizable material which has been permanently magnetized, or it may be composed of that other class of materials such as soft iron, steel, etc. which had previously been subjected to an electric field and contains a small amount of residual magnetism. Then the contacts of the male plug are inserted into an ordinary live female plug to become electrically connected with an alternating current source of supply which generally is 110 or 220 volt 60 cycle'AC. Then one or more of the switches 21 are closed to bring in the desired number of lamps in the circuit and finally the switch 12 is closed to complete the circuit and then is opened when desired. Upon closing of the switch 12, alternating current flows through the circuit comprising one or more of the incandescent lamps 20 in series with the coil 10; and when this circuit is initially made upon closing of switch 12 there occurs ahigh amperage surge through the coil 10 for only a very short period of time to establish for such a very short period of time a relatively high alternating flux field impressed directly upon the bar 40. The high amperage surge through coil 10 is due to the low initial resistance of the bank of lamps when the circuit is first made upon closing of switch 12 because the tungsten filamerits of said lamps are initially about at room temperature and therefore have low resistance characteristics. These lamps serve -to alternately control the resistance of the circuit and permit inrush current flow of a magnitude approximately ten times normal because the resistance of the lamp filaments greatly increases after the initial surge of the current therethrough which brings them to incandescent operating temperature. Consequently, substantially immediately after the filaments are brought to operating temperature and this occurs practically instantaneously upon closing of switch 12 due to the heavy inrush current flow in that circuit, the current in that circuit automatically decays and is reduced to about one-tenth that of the inrush current. Because the inrush current builds up so rapidly due to the very low inductance of the coil and due to the low-resistance of the lamp filaments, the lamp filaments become iucandmcent practically in; stantaneously upon making of the circuit and practically immediately thereafter the current flow in that circuit decays and is greatly reduced to normal due to the automatic change in resistance of the incandescent lamps. Consequently, the heavy inrush current does not flow through the coil for any appreciable length of time which would cause overheating and, therefore, small coils may be employed.

The following is a specific example given merely by way of illustration and is not to be taken by way of limit-ation of a specific design of the apparatus shown in Fig. 1 and a specific method for demagnetizing the bar 40 which may measure about 4" x 1" x 1". In this case the coil 10 has approximately 300 turns of insulated copper wire and measures approximately 4" in length. Four 300-watt, 110 volt tungsten filament incandescent lamps 20 are connected in parallel in the lamp bank through the switches 21, so that the inrush current through the coil 10 may be approximately 100 amperes.

By employing the foregoing procedure of placing in the circuit and connecting the male plug to the liv female plug and having the bar 40 surrounded by the coil 10, all that the operator need do is merely to close the switch 12 and then after a few seconds to open switch 12 and the bar 40 will be found to have been substantially completely demagnetized.

Instead of employing a coil 10 which extends substantially the full length of the bar 40, I may employ a shorter coil 41 such as that shown in Fig. 2. In this particular illustrative example, the coil 41 has a length which is but a fraction of the length of coil 10 and as shown is approximately one-third of the length of the bar 40. In this specific instance, the coil 41 measures about 1% in length and has approximately 100 turns of insulated copper wire. By employing the same elements as those of Fig. 1 except that coil 41 is substimted for coil 10 as shown in Fig. 2. Coil 41 may first be located at the lefthand end of bar 40 and the switches 21 and 12 are closed and opened in the sequence heretofore described. After the switch 12 is opened, the lefthand end of bar 40 will be found to have been substantially completely demagnetized. The coil 41 may be moved over to surround the next third length of the bar 40 and again the switches 21 and 12 are actuated in the same sequence as before. Finally the coil 41 is moved to the last third of the length of bar 40 and is then actuated in the same sequence as before. In this specific manner, the bar 40 will be substantially completely demagnetized.

If desired, two separate coils 31 may be employed in place of coil 10 with the coils connected in non-inductive relationship as shown and each being approximately two inches long and having approximately 150 turns of insulated copper wire. These two coils 31 in non-inductive relationship may be substituted for coil 10 of Fig. l and employed in the same manner as coil 10 in the practice of this invention. In the embodiments shown in Figs. 1-3, the bar 40 is located in the central opening through the coils and therefore is closely coupled with the flux field thereof upon energization of the coil. While it is preferable to have such relationship of parts for the purposes of demagnetization as herein provided, such disposit-ion of said elements is not always feasible or practical because of the shape of the material to be demagnetized or for some other reason. At a sacrifice of efliciency, bar 40 may be demagnetized by disposing it outside of the central opening through the coil 10, for example, and locating the bar 40 adjacent the outside of the coil. Instead of having the coil 10 an elongated element as shown in Fig. 1 it may be of toroidal shape as shown in Fig. 4 at 35 and may be disposed in the position shown in full lines with the bar 40 through the central opening of the coil or in the position shown in dotted lines with the bar 40 outside of the coil 35, and in either position serves the same purpose as coil 10 and may be substituted therefor. When a toroidal shaped coil such as 35 is employed, either in the position shown in full or dotted lines, I prefer to use it in the same manner as coil41. That is, by energizing the coil at one position, moving it to another position along the length of the bar, again energizing and so on. If the element 40 is of C or horse shoe shape, I prefer to encircle it with a toroidal shaped coil 36 and to energize the coil in the manner heretofore described at difierent positions along the length of the C-shaped element to assure demagnetization.

Since certain changes in carrying out the aforesaid methods and in the constructions set forth which embody the invention may be made without departing from its scope, it is intended that all matter contained in the description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all the generic and specific features of the invention herein described, and all statements of the scope of the invention which as a matter of language might be said to fall therebetween.

This application is a continuation in part of my copending application Serial No. 325,636, filed December 12, 1952, which is a continuation in part of my application Serial No. 140,744, filed January 26, 1950, and subsequently abandoned. I

I claim:

1. A demagnetizing apparatus comprising a source of A.C. current, a coil, a switch and resistance in series with each other, said resistance characterized by having a low resistance characteristic at room temperature when compared to its resistance characteristic at its incandescent temperature whereupon making of a circuit with the source of alternating current in series with said coil, switch and resistance provides a heavy inrush A.C. current through said coil for a very short period of time and decays to normal for demagnetizing a permanent magnet when located adjacent said coil.

2. A method for demagnetizing a material comprising locating said material in the central opening of a coil of a circuit comprising said coil, a source of alternating current and a filamentary resistance and aswitch in series with each other, said resistance having a resistivity at temperature of incandescence many times that at normal temperature, closing said switch to make said circuit, whereupon in-rush current flows through said resistance and said coil to practicallyinstantaneously raise the temperature of said resistance to incandescence and practically instantaneously thereafter the current in said circuit becomes automatically reduced to a lower value whereby said material in said opening is subject to the field created by said current passing through said coil to thereby demagnetize said material and then removing said material out of said opening.

References Cited in the file of this patent UNITED STATES PATENTS 

